This invention relates to a tempered glass sheet for vehicles, especially automobiles. This invention also relates to a window for vehicles, especially automobiles.
Recently, in vehicles, especially in automobiles, it is attempted to make the surfaces of windows smoother, that is, to reduce discontinuities between a vehicle body and a glass sheet, to reduce air resistance and wind noise. Smoothing the surfaces is effective in improving the appearance of vehicles. It is hard to fit an installing member as a resin molding into a window in which a windowpane is flush with a window frame without sticking out of the window. For removing a stepped portion formed by a installing member, therefore, resin panels having a worked edge have been proposed.
As shown in FIG. 15, Publication of Unexamined Japanese Patent Application Tokkai No. Sho 63-82814 discloses a resin panel 71 having a stepped edge. A retainer 73 is provided in a thin portion of the stepped edge. A resin molding 72 is fit to cover the top of the retainer 71 and have a flush surface with the resin panel 71. This resin panel 71 is installed into a window frame 75 with the retainer 73 and an adhesive 76.
As shown in FIG. 16, Publication of Unexamined Japanese Utility Model Application Zikko No. Hei 3-98115 discloses a resin panel 81 having a tapered edge. The tapered edge contributes to a smooth surface between the resin panel 81 and a resin molding 82 so that a flush surface of the window can be realized when installing the resin panel 81 into the window frame 85 with an adhesive 86. The tapered edge also makes it easy to form the panel 81 with a protecting film 83 by an injection molding method.
As shown in FIG. 17, Publication of Unexamined Japanese Patent Application Tokkai No. Hei 7-137535 discloses a resin panel 91 having a curved edge. The resin panel 91 is used for a retractable automatic window. The panel 91 can be moved along a guide rail from an opened position to a closed position in FIG. 17. The curved edge of the panel 91 makes the surface of the panel 91 flush with the window frame 95 when the panel 91 fits into a weather strip 92.
However, a resin panel has some problems in use as a windowpane, because the surface of a resin panel is easily damaged and a resin panel cannot keep sufficient transparency. A glass sheet is superior to a resin panel in transparency and surface hardness. On the other hand, a glass sheet may cause a problem in strength when working the edge of the glass sheet without any restriction as described above.
A glass sheet for a vehicle window is usually quenched for tempering since glass is brittle. For quenching, a glass sheet is heated to a temperature around its softening point. A tempered glass sheet produced by quenching has a compressive stress layer at the surface while a tensile stress layer appears in the central portion of the cross section. The presence of the compressive stress layer in the surface gives the tempered glass sheet strength. Therefore, when working the edge of the glass sheet to reduce its thickness, the effect of the partial change in thickness on the stress layers should be considered.
No investigations about the stepped edge in a tempered glass sheet for installing to a body of vehicles have been reported, since it has been thought that working in the edge of a tempered glass sheet should be avoided so as to keep the strength of the tempered glass sheet.
Therefore, in the field of glass windows for vehicles, as shown in FIG. 18, a molding 52 molded by extruding has been proposed to achieve a glass window for vehicles in which a glass sheet 51 is arranged flush with a vehicle body 53. This molding 52 is molded by extruding a resin directly at an edge of the glass sheet by remote control.
In addition, in the glass window for vehicles, as shown in FIG. 18, a ceramic mask 55 often is formed in the peripheral portion of the glass sheet. The ceramic mask 55 is formed so as to cover an attaching member, electrical equipment or the like around the window frame so that the appearance of the vehicle body is better. Generally, the ceramic mask 55 is formed in the following manner. A paste comprising a pigment, a glass frit or the like is printed in a predetermined region on the surface of the glass sheet by silk screen. Then, the glass sheet is heated so that the paste is fired in the predetermined region on the surface.
In the glass window for vehicles shown in FIG. 18, the flush surface is achieved by forming the molding 52 so as to be in contact with only the end face of the glass sheet 51. In this glass window, the ceramic mask 55 is required to be formed in the edge of the peripheral region (peripheral edge) 56 of the glass sheet. This is because the molding 52 fails to cover the vicinity of the peripheral edge of the glass sheet 51. However, it is not easy to print a paste while positioning the ceramic mask so that the end of the region where the ceramic mask is formed matches the peripheral edge of the glass sheet (i.e., to perform so-called just edge print). The paste may drop from the end face of the glass sheet, thus resulting in a defect. In addition, since the silk screen touches the corners of the glass sheet when printing, the life of the screen is shortened.
With the foregoing in mind, it is a purpose of the present invention to provide a tempered glass sheet for vehicle windows that has a sufficient strength needed for a windowpane and can be utilized for smoothing the surfaces of the window.
To achieve the above purpose, a tempered glass sheet for vehicles of the present invention has a stepped portion at least a part of a peripheral portion of the tempered glass sheet. The tempered glass sheet is produced by tempering a glass sheet, and the stepped portion is formed by reducing thickness relative to the thickness of the glass sheet. The tempered glass sheet has a thin portion and a thick portion formed by the stepped portion. A difference in thickness between the thin portion and the thick portion is 0.5 mm or more, and the thickness of the thin portion is thicker than half the thickness of the thick portion.
Thus, a tempered glass sheet having such a worked peripheral portion as described above is suitable for a vehicle window since the glass sheet has a sufficient strength needed for a windowpane and can be utilized for smoothing the window, that is, reducing discontinuities between the vehicle body and the windowpane.
A window for vehicles of the present invention comprises the tempered glass sheet and a supporting member for attaching the tempered glass sheet to a body of a vehicle. It is preferable that the supporting member is fitted in the stepped portion and the supporting member is substantially flush with the tempered glass sheet.